1) Field of the Disclosure
The disclosure relates generally to composite materials and methods, and more particularly, to hybrid composite laminates and methods for use in composite structures, such as aircraft, spacecraft, and other vehicles.
2) Description of Related Art
Composite structures and component parts are used in a wide variety of applications, including in the manufacture of aircraft, spacecraft, rotorcraft, watercraft, automobiles, trucks, and other vehicles. In particular, in aircraft construction, composite structures and component parts are used in increasing quantities to form the fuselage, wings, tail section, skin panels, and other component parts of the aircraft.
Known methods exist for fabricating hybrid laminates that combine polymeric composite materials, such as graphite, boron, or a blend of graphite and boron composite, and metal foil materials, such as, titanium. The metal foil material may be added between laid up plies of polymeric composite unidirectional tape. For example, U.S. Pat. No. 5,866,272 to Westre et al., incorporated by this reference, is one of several patents teaching the placement of titanium foil between plies of polymeric composite unidirectional tape.
However, known composite and hybrid laminate materials can only leverage the strengthening fibers that are in the load path and do not leverage the strength of off-axis fibers. Moreover, known composite and hybrid laminate materials may not be effective at providing a current dissipation path in the composite structure, for example, for effective lightning strike protection. In addition, known composite and hybrid laminate materials may not provide effective impact resistance from high impact sources, such as hail or bird strikes, without having to change the structure by cross stitching or increasing the thickness of the composite structure, to name a few methods. Further, known composite and hybrid laminate materials may not provide effective thermal impingement resistance from high energy thermal impingement sources, such as lasers and X-rays. In addition, known composite and hybrid laminate materials may not provide the ability to combine separate structural and electrical systems into a single system on an aircraft.
Moreover, lightweight composite designs, such as for keel beams in aircraft, may require additional structurally parasitic conductors to effectively disperse the current from a lightning strike. Such additional conductors can add weight to the aircraft, and can result in increased fuel costs and overall costs. Known composite and hybrid laminate materials may not provide the desired lightweight, high performing composite keel beam that may be effective in conducting current and acting as a lightning strike current return path.
In addition, when system penetrations, access paths, and other non-load bearing areas are needed in composite or hybrid composite panels or structures, it may be necessary to pad-up the lay-up to facilitate the transmission of load around these areas. Known composite and hybrid laminate materials may be utilized to provide extra thickness which may result in additional cost, part volume and weight to the composite structure.
Moreover, thermal and temperature uniformity and the ability to control excessive thermal energy due to cure kinetics of the resins are important fabrication issues when curing thermosetting composites. Thermal and temperature control of the curing cycle may preclude the use of some composite configurations.
Further, repair areas of composite structures may need a significant increase in thickness of the composite structure to restore the composite structure to at least its original strength. This may cause additional aerodynamic drag and may also affect the appearance of the composite structure.
Further, during fabrication of composite parts, the plies of an uncured composite part having a uniform cross section may wrinkle at one or more areas where a cured or pre-cured composite part having a non-uniform cross section is joined to the uncured composite part. Such wrinkling of the plies may be due to differences in pressure between the cured or pre-cured composite part and the uncured composite part at the joined areas. Such wrinkling of the plies may result in fiber distortion of the composite material in the uncured composite part.
Finally, determination of initiation and propagation of flaws in composite structures is important in predicting service life and maintenance of the composite structure. Known composite and hybrid laminate structures are typically replaced or repaired at certain intervals. Such intervals are by their nature conservative, which may lead to additional, potentially unnecessary, cost accrual.
Accordingly, there is a need in the art for hybrid composite laminates and methods that provide advantages over known composite materials and known hybrid composite laminates and methods.